I know it's hard, but you cannot treat your partner like a psychiatric support unit. Your three-step system relies on a third-party's cooperation, and your partner has made it clear that he is not going to be able to cooperate every single time. That means, you either need to expand your support network or (better) start working on dealing with your episodes by yourself. CBT might be something to look into: it's often useful for people trying to manage anxiety or distorted thinking that lead to emotional problems.

You frame it like he's withholding what you want out of callousness ("if he wishes"), but he has emotional limits too. And think about it from his perspective: dealing with your episodes is exhausting and doesn't really fix anything, just a temporary band-aid that drains his time and energy. Sometimes, he's just not in a position to help you the way you want. He has his own life, his own stresses, his own mental burdens. Your episodes are going to pass, whether he plays along or not, and he probably knows that. You also have to know that, if the thoughts that are causing your feelings are irrational, it's going to be next to impossible for anyone to understand what's going on in your head. By definition, it makes no sense.

I say all this as the one in my relationship that has the mental illness issues (the oh-so-common anxiety/depression cocktail). You have to step up and learn to manage them yourself. It's great when partners can support us--your boyfriend sounds like he's happy to, insofar as his own emotional limits will allow--but we can't hinge our treatment on anyone but ourselves. It's weird to me that your three steps are the same as the steps for dealing with panic attacks (which I get)...except for the third step, which in your case involves asking someone else to help you. The third step usually is "make yourself comfortable", not "get someone else to make you feel better". For me, my third step is excusing myself, finding a quiet place and doing my CBT journaling, with a cup of tea or a diet coke. No third party required.

Of course, I'm not telling you not to feel resentful. You can leave your relationship if you feel dissatisfied and uncared for. But no partner is ever going to be 100% there for you 100% of the time, and that's why its critical for those of us with mental issues to learn how to handle our business.